We just returned from the Fairmont. We actually flew out late Sunday night (I think that was the 19th or so) on an "evacuation" flight, added by Jetblue, in advance of Dean.
We were there for almost ten days and rented a car upon arrival from Avis at the airport. Frankly, if you want to explore a bit renting a car really is your best option. Avis was very good, even when I had some issues with the first car I received. Even if you get a good rental rate, however, insurance can add up. I believe there have been many postings on whether you need/want additional insurance in Mexico for a rental car. We've traveled to Mexico for many years (used to live there briefly) and thought the extra cost was worth the peace of mind.
You can get a car service from the airport to the Mayakoba for about $60 each way and then rent a car for a day or so once at the hotel but, at the end of the day, I think renting the car from the start makes more sense. The hotel does charge daily for parking, however.
The hotel is beautiful, and very new. Winding paths, canals and much vegetation. It reminded us a bit of SEAsia. Hopefully, Dean did not affect it much. The hotel is very spread out, but there are golf cart-like buggies running constantly, there are bikes available to ride around and you can certainly walk everywhere. Service was mostly excellent, on par with some Four Seasons. Friendly, attentive and caring. When asked for directions most workers (as taught at Ritz Carlton) would accompany you to the destination. Certainly, it is the nicest hotel in the area for now. The Mandarin is supposed to open next door in a few months, and a Banyan Tree on the other side of the Fairmont in a year or so.
With a car you can also head into PDC for dining. Its an easy ten minute drive. There are some good (not great) restaurants in PDC. The rule of thumb seems to be the simpler the better. And the more local the better. The food at the hotel was Ok, but the food off premise, as expected, was more interesting and less expensive. We thought bkfst was the best meal at the hotel.
Tulum is about an hour or less south of the hotel on an easy highway drive. It is worth the trip, and can be toured in a couple of hours easily. On the way back you can stop at Akumal, a small town with a beautiful beach.
Have fun. Let me know if you need other info.